Fluorescent compounds and their applications are well known. For example, a group of organic fluorescent compounds generally referred to as coumarins, or another group generally referred to as rhodamines, are used at relatively low concentration in a suitable solvent in so-called dye-laser applications. Fluorescent compounds also find application as optical brighteners in fabrics and papers. Fluorescent compounds are also employed as radiation converters in medical radiology and as scintillation agents for detecting low level radiation.
In the above applications, fluorescent compounds are more or less uniformly dissolved, dispersed, imbibed or deposited in the liquid, or in or on the article, such as a fabric fiber or paper stock.
More recently, the use of fluorescent compounds dissolved in polymeric, organic, film-forming materials has been reported. In U.S. Pat. No. 4,262,206 by W. Viehmann is disclosed a fluorescent radiation converter, comprising a more or less uniform coating on a substantially transparent support of a polymeric material containing a fluorescent compound.
Other applications of unpatterned fluorescent coatings relate to their use in conjunction with solid-state radiation-sensing elements, such as silicon-based photovoltaic sensors or charge-coupled devices (CCD). Here, the unpatterned fluorescent, polymeric coating is applied more or less uniformly on an individual device for the purpose of extending the responsivity of the device to a spectral region or wavelength range where the native, uncoated device has little or no response to incident radiation.
Such applications of unpatterned, fluorescent polymeric coatings over radiation-sensitive elements are disclosed in: U.S. Pat. No. 4,605,849 by P. O. Kliem; W. Viehmann, et al, SPIE Vol. 279, "Ultraviolet and Vacuum Ultraviolet Systems", pages 146-152 (1981); F. E. Stuart, et al, SPIE Vol. 331, "Instrumentation in Astronomy IV", pages 52-68 (1982), and references contained therein.
U.S. Pat. No. 4,577,098 by K. Ogawa discloses a solid-state imager with inorganic fluorescent elements. Patterned fluorescent elements are inferred, but no teaching is provided about the patterning of such inorganic fluorescent elements.